1 /*
2 * High memory handling common code and variables.
3 *
4 * (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
5 * Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
6 *
7 *
8 * Redesigned the x86 32-bit VM architecture to deal with
9 * 64-bit physical space. With current x86 CPUs this
10 * means up to 64 Gigabytes physical RAM.
11 *
12 * Rewrote high memory support to move the page cache into
13 * high memory. Implemented permanent (schedulable) kmaps
14 * based on Linus' idea.
15 *
16 * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
17 */
18
19 #include <linux/mm.h>
20 #include <linux/module.h>
21 #include <linux/swap.h>
22 #include <linux/bio.h>
23 #include <linux/pagemap.h>
24 #include <linux/mempool.h>
25 #include <linux/blkdev.h>
26 #include <linux/init.h>
27 #include <linux/hash.h>
28 #include <linux/highmem.h>
29 #include <linux/blktrace_api.h>
30 #include <asm/tlbflush.h>
31
32 /*
33 * Virtual_count is not a pure "count".
34 * 0 means that it is not mapped, and has not been mapped
35 * since a TLB flush - it is usable.
36 * 1 means that there are no users, but it has been mapped
37 * since the last TLB flush - so we can't use it.
38 * n means that there are (n-1) current users of it.
39 */
40 #ifdef CONFIG_HIGHMEM
41
42 unsigned long totalhigh_pages __read_mostly;
43 EXPORT_SYMBOL(totalhigh_pages);
44
nr_free_highpages(void)45 unsigned int nr_free_highpages (void)
46 {
47 pg_data_t *pgdat;
48 unsigned int pages = 0;
49
50 for_each_online_pgdat(pgdat) {
51 pages += zone_page_state(&pgdat->node_zones[ZONE_HIGHMEM],
52 NR_FREE_PAGES);
53 if (zone_movable_is_highmem())
54 pages += zone_page_state(
55 &pgdat->node_zones[ZONE_MOVABLE],
56 NR_FREE_PAGES);
57 }
58
59 return pages;
60 }
61
62 static int pkmap_count[LAST_PKMAP];
63 static unsigned int last_pkmap_nr;
64 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
65
66 pte_t * pkmap_page_table;
67
68 static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
69
flush_all_zero_pkmaps(void)70 static void flush_all_zero_pkmaps(void)
71 {
72 int i;
73 int need_flush = 0;
74
75 flush_cache_kmaps();
76
77 for (i = 0; i < LAST_PKMAP; i++) {
78 struct page *page;
79
80 /*
81 * zero means we don't have anything to do,
82 * >1 means that it is still in use. Only
83 * a count of 1 means that it is free but
84 * needs to be unmapped
85 */
86 if (pkmap_count[i] != 1)
87 continue;
88 pkmap_count[i] = 0;
89
90 /* sanity check */
91 BUG_ON(pte_none(pkmap_page_table[i]));
92
93 /*
94 * Don't need an atomic fetch-and-clear op here;
95 * no-one has the page mapped, and cannot get at
96 * its virtual address (and hence PTE) without first
97 * getting the kmap_lock (which is held here).
98 * So no dangers, even with speculative execution.
99 */
100 page = pte_page(pkmap_page_table[i]);
101 pte_clear(&init_mm, (unsigned long)page_address(page),
102 &pkmap_page_table[i]);
103
104 set_page_address(page, NULL);
105 need_flush = 1;
106 }
107 if (need_flush)
108 flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
109 }
110
111 /**
112 * kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
113 */
kmap_flush_unused(void)114 void kmap_flush_unused(void)
115 {
116 spin_lock(&kmap_lock);
117 flush_all_zero_pkmaps();
118 spin_unlock(&kmap_lock);
119 }
120
map_new_virtual(struct page * page)121 static inline unsigned long map_new_virtual(struct page *page)
122 {
123 unsigned long vaddr;
124 int count;
125
126 start:
127 count = LAST_PKMAP;
128 /* Find an empty entry */
129 for (;;) {
130 last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
131 if (!last_pkmap_nr) {
132 flush_all_zero_pkmaps();
133 count = LAST_PKMAP;
134 }
135 if (!pkmap_count[last_pkmap_nr])
136 break; /* Found a usable entry */
137 if (--count)
138 continue;
139
140 /*
141 * Sleep for somebody else to unmap their entries
142 */
143 {
144 DECLARE_WAITQUEUE(wait, current);
145
146 __set_current_state(TASK_UNINTERRUPTIBLE);
147 add_wait_queue(&pkmap_map_wait, &wait);
148 spin_unlock(&kmap_lock);
149 schedule();
150 remove_wait_queue(&pkmap_map_wait, &wait);
151 spin_lock(&kmap_lock);
152
153 /* Somebody else might have mapped it while we slept */
154 if (page_address(page))
155 return (unsigned long)page_address(page);
156
157 /* Re-start */
158 goto start;
159 }
160 }
161 vaddr = PKMAP_ADDR(last_pkmap_nr);
162 set_pte_at(&init_mm, vaddr,
163 &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
164
165 pkmap_count[last_pkmap_nr] = 1;
166 set_page_address(page, (void *)vaddr);
167
168 return vaddr;
169 }
170
171 /**
172 * kmap_high - map a highmem page into memory
173 * @page: &struct page to map
174 *
175 * Returns the page's virtual memory address.
176 *
177 * We cannot call this from interrupts, as it may block.
178 */
kmap_high(struct page * page)179 void *kmap_high(struct page *page)
180 {
181 unsigned long vaddr;
182
183 /*
184 * For highmem pages, we can't trust "virtual" until
185 * after we have the lock.
186 */
187 spin_lock(&kmap_lock);
188 vaddr = (unsigned long)page_address(page);
189 if (!vaddr)
190 vaddr = map_new_virtual(page);
191 pkmap_count[PKMAP_NR(vaddr)]++;
192 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
193 spin_unlock(&kmap_lock);
194 return (void*) vaddr;
195 }
196
197 EXPORT_SYMBOL(kmap_high);
198
199 /**
200 * kunmap_high - map a highmem page into memory
201 * @page: &struct page to unmap
202 */
kunmap_high(struct page * page)203 void kunmap_high(struct page *page)
204 {
205 unsigned long vaddr;
206 unsigned long nr;
207 int need_wakeup;
208
209 spin_lock(&kmap_lock);
210 vaddr = (unsigned long)page_address(page);
211 BUG_ON(!vaddr);
212 nr = PKMAP_NR(vaddr);
213
214 /*
215 * A count must never go down to zero
216 * without a TLB flush!
217 */
218 need_wakeup = 0;
219 switch (--pkmap_count[nr]) {
220 case 0:
221 BUG();
222 case 1:
223 /*
224 * Avoid an unnecessary wake_up() function call.
225 * The common case is pkmap_count[] == 1, but
226 * no waiters.
227 * The tasks queued in the wait-queue are guarded
228 * by both the lock in the wait-queue-head and by
229 * the kmap_lock. As the kmap_lock is held here,
230 * no need for the wait-queue-head's lock. Simply
231 * test if the queue is empty.
232 */
233 need_wakeup = waitqueue_active(&pkmap_map_wait);
234 }
235 spin_unlock(&kmap_lock);
236
237 /* do wake-up, if needed, race-free outside of the spin lock */
238 if (need_wakeup)
239 wake_up(&pkmap_map_wait);
240 }
241
242 EXPORT_SYMBOL(kunmap_high);
243 #endif
244
245 #if defined(HASHED_PAGE_VIRTUAL)
246
247 #define PA_HASH_ORDER 7
248
249 /*
250 * Describes one page->virtual association
251 */
252 struct page_address_map {
253 struct page *page;
254 void *virtual;
255 struct list_head list;
256 };
257
258 /*
259 * page_address_map freelist, allocated from page_address_maps.
260 */
261 static struct list_head page_address_pool; /* freelist */
262 static spinlock_t pool_lock; /* protects page_address_pool */
263
264 /*
265 * Hash table bucket
266 */
267 static struct page_address_slot {
268 struct list_head lh; /* List of page_address_maps */
269 spinlock_t lock; /* Protect this bucket's list */
270 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
271
page_slot(struct page * page)272 static struct page_address_slot *page_slot(struct page *page)
273 {
274 return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
275 }
276
277 /**
278 * page_address - get the mapped virtual address of a page
279 * @page: &struct page to get the virtual address of
280 *
281 * Returns the page's virtual address.
282 */
page_address(struct page * page)283 void *page_address(struct page *page)
284 {
285 unsigned long flags;
286 void *ret;
287 struct page_address_slot *pas;
288
289 if (!PageHighMem(page))
290 return lowmem_page_address(page);
291
292 pas = page_slot(page);
293 ret = NULL;
294 spin_lock_irqsave(&pas->lock, flags);
295 if (!list_empty(&pas->lh)) {
296 struct page_address_map *pam;
297
298 list_for_each_entry(pam, &pas->lh, list) {
299 if (pam->page == page) {
300 ret = pam->virtual;
301 goto done;
302 }
303 }
304 }
305 done:
306 spin_unlock_irqrestore(&pas->lock, flags);
307 return ret;
308 }
309
310 EXPORT_SYMBOL(page_address);
311
312 /**
313 * set_page_address - set a page's virtual address
314 * @page: &struct page to set
315 * @virtual: virtual address to use
316 */
set_page_address(struct page * page,void * virtual)317 void set_page_address(struct page *page, void *virtual)
318 {
319 unsigned long flags;
320 struct page_address_slot *pas;
321 struct page_address_map *pam;
322
323 BUG_ON(!PageHighMem(page));
324
325 pas = page_slot(page);
326 if (virtual) { /* Add */
327 BUG_ON(list_empty(&page_address_pool));
328
329 spin_lock_irqsave(&pool_lock, flags);
330 pam = list_entry(page_address_pool.next,
331 struct page_address_map, list);
332 list_del(&pam->list);
333 spin_unlock_irqrestore(&pool_lock, flags);
334
335 pam->page = page;
336 pam->virtual = virtual;
337
338 spin_lock_irqsave(&pas->lock, flags);
339 list_add_tail(&pam->list, &pas->lh);
340 spin_unlock_irqrestore(&pas->lock, flags);
341 } else { /* Remove */
342 spin_lock_irqsave(&pas->lock, flags);
343 list_for_each_entry(pam, &pas->lh, list) {
344 if (pam->page == page) {
345 list_del(&pam->list);
346 spin_unlock_irqrestore(&pas->lock, flags);
347 spin_lock_irqsave(&pool_lock, flags);
348 list_add_tail(&pam->list, &page_address_pool);
349 spin_unlock_irqrestore(&pool_lock, flags);
350 goto done;
351 }
352 }
353 spin_unlock_irqrestore(&pas->lock, flags);
354 }
355 done:
356 return;
357 }
358
359 static struct page_address_map page_address_maps[LAST_PKMAP];
360
page_address_init(void)361 void __init page_address_init(void)
362 {
363 int i;
364
365 INIT_LIST_HEAD(&page_address_pool);
366 for (i = 0; i < ARRAY_SIZE(page_address_maps); i++)
367 list_add(&page_address_maps[i].list, &page_address_pool);
368 for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
369 INIT_LIST_HEAD(&page_address_htable[i].lh);
370 spin_lock_init(&page_address_htable[i].lock);
371 }
372 spin_lock_init(&pool_lock);
373 }
374
375 #endif /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */
376